Is it possible to print a high narrow shape without support?

(it’s a pity that I cannot upload a picture to show better what I want to say)

Hello, I’m architect working in Paris and I have a question about printability.

Print conditions,

  • Form 3
  • Resin Formlabs white V4
  • Layer thinkness 0.1mm (we are also considering to buy the draft resin and print at 0.2mm)

The shapes we want to print are “triangular profiles” that are “slightly curved”.
The triangular profiles are about 25mm by 20mm and the profiles are about 170mm long in vertical.
The face of all shape are cut by a plane and they are oriented to be perfectly on the surface.

In preform, even without support, “Show Minima” and “Show Cups” are in green.
But “Printability” is in yellow (Warning)

By my experiences, printing directly on the bed is not bad when it’s a clean surface. (that is the case in our model)
Also, there are no parts where the resin can stag to make a detachement while the model moves up and down.
There are no weak points because the width are quite uniform.

But since the shapes are quite long in vertical I wonder if the surface touching the bed will be enough to maintain the model while printing.

Can you share your experiences to give me some ideas?
Thank you!!

It’s worth a shot. In my experience the Form 3 has pretty strong adhesion (much stronger than I ever used on the Form 2). I agree a 2.5cm x 2cm square might be a tad smaller than I’d like for a 17cm tall tower, but my gut feeling is it would probably work (especially using a Standard resin). If you do run into adhesion troubles, I’m told roughing up the build platform with a bit of sandpaper can also help improve adhesion (search the forums to find the grit people are using - just make sure to wipe off all debris before using).

Thanks a lot.
I wanted to try this but just the next day after I posted this question, our boss decided to change the method. I hope next time I will have a chance to test it to see if it work or not.

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It’s too bad you won’t get to try it; but, in my experience the base platform has good adhesion for all resin types over the volume of the printer. That is, the printer was designed with a 185mm print depth, and the expectation is that the platform can support models that fit in the volume and pass printability checks.

Printing directly on the bed vs printing with a raft doesn’t really matter as far as adhesion goes. There’s nothing special about the rafts other than that they’re generated to cover the whole area under supports. The little lips on the edges of the rafts help with removal, though. My only advice about printing directly on the bed is to be careful when removing your parts, if the adhesion is high you risk cracking the part if you’re aggressive.

Here’s a way to maximize your chances, though (nothing is ever guaranteed):

  1. Load and orient your model in PreForm.
  2. Open the supports dialog, for raft type choose None. Do not generate supports.
  3. Edit the supports for the model. This will trigger the support analysis, which will turn areas red that need more support. Check to make sure you don’t have any red areas (or the red that’s there is acceptable).

For example, here’s a bunch of rectangles at various angles. This shows that some of the steeper ones might have issues:

One thing you can do if you really don’t trust your contact area is model a slightly wider base in your parts, then just cut it off after printing is finished (you can model a little groove or something at the top of your base to help you cut it more precisely in post). Then you’ll have a greater contact area. Maybe something like:

Still… the tricky part in my opinion, though (in general without seeing your model), isn’t so much adhesion as it is flex. If your structure is fairly well-balanced then all is good, but if it’s off balance and starts to flex to one side as it’s being built, then the layers will end up skewed, or the part could even crack itself off the platform. You kind of just have to go with your gut. If it doesn’t look like the model can stay stable, you can sometimes add support structures on the sides.

I mean, in the above pic, at that point you might as well just generate supports, too. Then you can sand off the touchpoints after printing.

Tough 2000 has (infamously) better adhesion than the standard resins if you’re worried. The Gray Pro, Tough, and Rigid resins are stiffer than the standard ones, if that becomes an issue (in particular, the Rigid resins are rock solid even for very thin parts, although they are brittle; sort of like a ceramic or glass kind of vibe).

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